None of this code can be reached any more, so it can all be removed

Bootsnap speeds up Rails loading and now ships by default with Rails 5.2
apps. We should promote this to a default gem and test it out in
production. This will also make it possible for the Helm Charts to take
advantage of this.

It appears that Bootsnap with Rails 5.2.3 and all the GitLab CE gems
loads fine on an ARM platform now, so it's possible that
https://gitlab.com/gitlab-org/gitlab-ce/issues/34799 has been resolved.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/45230

peek-redis resets its counters at the start of an ActionController
notification (`start_processing.action_controller`), which causes it to
miss some Redis queries that precede it, such as the database load
balancer and Rack Attack queries. This produces inconsistencies in the
performance bar between the number of calls and their durations with the
actual calls in the detailed view.

We fix this by getting rid of peek-redis in favor of consolidating all
logic into the `RedisDetailed` view, which tracks Redis queries using
`RequestStore`. This has the nice property of removing thread-specific
counters as well.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/64707

This will make it possible for Oracle Cloud to work with S3 by disabling
Signature V4 streaming (https://github.com/fog/fog-aws/issues/523).

Full CHANGELOG:
https://github.com/fog/fog-aws/blob/master/CHANGELOG.md

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/63041

This was done to perform some local testing, but while the change was
already made it made sense to commit the change.

Updates changed method names and fixes spec failures

Adds more friendly docs for GraphQl implementation

This brings the rspec-core version in line with the Gitaly changes
and introduces Rails 5.1/5.2 improvements.

Full CHANGELOG:
https://github.com/rspec/rspec-rails/blob/master/Changelog.md

Update net-ssh gem to ~> 5.2

See merge request gitlab-org/gitlab-ce!30341

The configuration is currently only specified in CI, by moving it into
`.mdlrc` we get immediate feedback locally in supported editors.

To ensure `mdl` is available it's also added to the `Gemfile`, though
CI will still use the version installed in the `gitlab-docs-lint` image.